1. Field of the Invention
The present invention relates to a rear-seat occupant protection apparatus designed to protect an occupant seated in a rear seat.
2. Description of the Background Art
Heretofore, there has been known a vehicle occupant protection apparatus which comprises an acceleration sensor adapted to detect a collision of a vehicle based on an acceleration of the vehicle, a lower-leg restraint unit (active bolster) adapted to restrain a lower leg of an occupant, a drive unit adapted, in response to receiving an output signal of the acceleration sensor, to actuate the lower-leg restraint unit, wherein the lower-leg restraint unit is disposed in a seat back of a front seat to restrain a lower leg of an occupant seated in a rear seat located behind the front seat, during a frontal collision of the vehicle, as disclosed, for example, in JP 2004-224241A.
The vehicle occupant protection apparatus as disclosed in the above patent document has an advantage of being able to restrain a lower leg of an occupant seated in a rear seat during a frontal collision of a vehicle to thereby suppress an amount of displacement of the occupant seated in the rear seat in a frontward direction of the vehicle.
However, in the technique of restraining only the lower leg of the rear-seat occupant during the frontal collision of the vehicle, as disclosed in the above patent document, there is a problem that a possibility of occurrence of the following undesirable situation cannot be denied. For example, if a relatively large impact load (inertia force) is applied to the rear-seat occupant due to the frontal collision of the vehicle, an upper body of the rear-seat occupant is significantly lunged frontwardly to cause a head of the rear-seat occupant to strike the seat back of the front seat, and thereby a large impact is applied to the head of the rear-seat occupant.